| Title | Fracture Spacing, Matrix Permeability, and Mechanical Feedbacks: Key Drivers of Heat Recovery in Geothermal Reservoirs |
|---|---|
| Authors | Hamid Nick |
| Year | 2026 |
| Conference | World Geothermal Congress |
| Keywords | Fracture dynamics; Heat transport; THM coupling |
| Abstract | This study explores the interplay of thermal-hydraulic-mechanical (THM) processes in fractured geothermal reservoirs, focusing on how fracture geometry, injection rate, and matrix permeability influence heat transport and system performance. A fully coupled finite element model is used to simulate non-isothermal flow and mechanical deformation in both the rock matrix and fracture networks. Cold fluid injection and hot fluid production are modeled in a doublet system under various reservoir conditions. Results show that fracture aperture variation, driven by thermal contraction of the rock matrix, affects flow pathways and thermal breakthrough. In low-density fracture networks, this effect is more pronounced, leading to early cold-water breakthrough and reduced heat exchange. Increments in fracture spacing and/or pumping rates decrease system performance, as reflected in temperature development, pressure requirements, and all evaluated key performance indicators (KPIs). At high fracture spacing and low matrix permeability, fracture networks act as hydraulic short-circuits, bypassing the matrix and reducing thermal interaction. A global sensitivity analysis highlights the critical role of THM coupling in accurately predicting reservoir behavior. Importantly, neglecting mechanical processes in performance predictions leads to overestimation of heat extraction, particularly in reservoirs with low matrix permeability. These reservoirs are also more susceptible to fracture deformation, which further reduces fracture–matrix thermal interaction and overall heat recovery. |